Mechanisms for reeling wire, tape and the like

ABSTRACT

A magnetic wire recording device with two sets of coaxial reels. One reel in each set is positively driven while the other is driven via a slipable clutch so arranged as to maintain constant tension in the wire. One set of reels winds while the other set rewinds, and the drive is automatically reversed by a switch which operates when an unwinding reel becomes empty.

United States Patent Inventor Roland William Gordon SomervellBeaconslield, England Appl. No. 718,302 Filed Mar. 18, 1968 PatentedFeb. 2, 1971 Assignee S. Davall & Sons Limited Middlesex, England aBritish Company Priority Apr. 28, 1967 Great Britain 19690/67 MECHANISMSFOR REELING WIRE, TAPE AND THE LIKE Primary ExaminerGeorge F. MautzAttorney-Mawhinney & Mawhinney ABSTRACT: A magnetic wire recordingdevice with two sets of coaxial reels. One reel in each set ispositively driven while 13 Claims 16 Drawing Figs the other is drivenvia a slipable clutch so arranged as to main- U.S. Cl 242/54.1, tainconstant tension in the wire. One set of reels winds while 242/57,242/158.5, 242/193 the other set rewinds, and the'drive is automaticallyreversed Int. Cl Gllb /32, by a switch which operates when an unwindingreel becomes B65h /32, B65h 54/78 empty.

MECHANISMS FOR REELING WIRE. TAPE AND THE LIKE This invention relates tomechanisms for reeling wire. tape or like extended members.

The invention provides a mechanism for reeling wire. tape or a likeextended member off from a reel onto another reel, in which thearrangement is such that the maximum diameter at which the extendedmember is wound onto one rcel is less than the minimum diameter at whichthe extended member is wound off the other reel, reversible drive meansare coupled to the said one reel and via a slipable clutch to the saidother reel which is acted upon by brake means, the drag torque of thebrake means exceeding the drive torque of the slipable clutch for drivein the sense in which the extended member is wound onto the said onereel from the said other reel and the drive torque of the slipableclutch exceeding the drag torque of the brake means for drive in theopposite sense.

Preferably the two reels are coaxially mounted.

Preferably the slipable clutch and preferably also the brake meanscomprise stepped helical coil springs acting between the reels andbetween a supporting frame member and the said other reel respectively.

Preferably the slipable clutch comprises a stepped helical coil springthe larger diameter end of which engages the inwardly facing surface ofa bore in the said one reel and the smaller diameter end of whichengages around a cylindrical surface on the said other reel.

Preferably the brake means comprises a stepped helical coil spring ofopposite hand to that comprising the slipable clutch, the smallerdiameter end of which stepped helical coil spring engages around anothercylindrical surface on the said other reel and the larger diameter endof which engages the inwardly facing surface of a bore in the framemember.

Preferably the mechanism is incorporated in a magnetic wire recordingmechanism and preferably means are provided for automatically reversingthe direction of drive to the said one reel after a predetermined amountof reeling from one reel onto the other has taken place.

The invention also provides guide pulleys for guiding wire tape or alike extended member off from one reel onto a coaxially mounted reel,which guide pulleys are mounted on a single platform reciprocated tocause the extended member to form into, or run easily from, even axiallyextending layers on the reels.

Preferably the setting of relative location and/or orientation of theplatform and reels is adjustable for applying correction to layeringfaults.

The invention also provides an automatic switching device in a mechanismfor reeling wire, tape or a like extended member comprising a switchmember on a reel which switch member is biassed into a switch actuatingposition out of which the switch member is held against the bias byextended member wound on the reel, whereby when the last layer ofextended member unwinds from holding the switch member as aforesaid, theswitch member is released.

Preferably, where wire is wound off from one reel onto another reel, theautomatic switching device is arranged to reverse the drive to the reelswhen the switch member is released.

The invention also provides an electrical switching device comprising anoperating member and an operated member both of which are arranged andbiassed to be movable over center with a toggle action between off andon conditions, and coupling between the members arranged so that theoperating member only acts upon the operated member to move the operatedmember over center after the operating member has moved over center.

A specific construction of magnetic wire recording device embodying theinvention will now be described by way of example and with reference tothe accompanying drawings, in which:

FIG. 1 is a sectional view, partly diagrammatic, of part of themechanism;

FIG. 2 is a diagrammatic perspective view of a stopped helical coilspring;

FIG. 3 is a side elevation of the mechanism with some parts omitted;

FIG. 4 is a plan view of the mechanism with some parts omitted;

FIGS. 5, 6 and 7 are diagrammatic plan views of part of the mechanismshown respectively in three different conditions;

FIG. 8 is a diagrammatic side view of the part shown in FIGS. 5, 6 and 7and FIGS. 9 to 16 are diagrammatic representations of wire layeringconditions on the four reels of the mechanism of this example.

In this example the magnetic wire recording device 11 comprises fourreels 12. 13. 14. 15 mounted coaxially on a shaft 16. In this examplethe arrangement of four reels provides two magnetic wire reeling deviceswhich operate simultaneously from one reversible drive coupled to gearwheel 17.

Magnetizable wire 18 stored on reels l2 and 13 is guided off one reelonto the other by two pulleys 19, 21 mounted on a tilted platform 22(see FIGS. 3 and 4). The platform 22 also supports three recording heads23 past which the wire is guided. The same platform 22 also supportsguide pulleys 24, 25 for the wire 26 of the reels 14, 15 and threerecording heads 27 for this lower reeling mechanism.

The pulleys 19, 21 are mounted on a plate 28 secured to the platform 22so as to be laterally adjustable on the platform 22 as indicated by thearrows 29 in FIG. 4. The recording heads 23 are also mounted on theplate 28 and the position of each recording head is adjustable on theplate 28 as indicated by the arrows 31 in FIG. 4. This adjustability ofthe heads 23 on the plate is necessary for securing correct location ofthe heads in relation to the wire 18.

The pulleys 24, 25 and recording heads 27 are similarly mounted on aplate 32 also secured to the platform 22 so as to be laterallyadjustable in the same manner as plate 28.

The platform 22 is pivoted on a shaft 33 and is coupled by means of abridge 34 to a cam follower block 35. A spherical roller 36 is rotatablymounted on a spigot 37 projecting from the cam follower block 35. Theroller 36 is acted upon by heart cam 38 to produce a cycled tilting ofthe platform 22 the extent of which tilting is indicated by arrows 39 inFIG. 3. Adjustment of the mean setting of tilt of the platform 22 isachieved by the adjustable relative location of the cam follower block35 and the bridge 34. As shown in FIG. 3, the block 35 is pivoted at 41to the bridge 34 and clamped by screws 42 received through slots in thebridge 34. The extent of the adjustment so provided of the mean tilt ofthe platform 22 is indicated by arrows 43 in FIG. 3.

The operation of the platform 22 and the effect of the severaladjustments is described more fully below with reference to FIGS. 9 to16.

As may best be seen in FIG. 1, the reel 12 is of larger diameter thanthe reel 13 and the arrangement is such that the diameter at which wire18 reels onto, or off from reel 12 is always greater than that at whichthe wire 18 reels onto, or off from reel 13. The reel 13 is keyed to thedrive shaft 16 by pin 44 while the reel 12 is mounted on bearings 45 forfree rotation on the shaft 16.

The slipable clutch connection between the reel 13 and the reel 12 isprovided by a right handed stepped helical coii spring 46. Brakingbetween the reel 12 and a frame member 47 is provided by a left handedstepped helical coil spring 48. The formation of these stepped helicalcoil springs is shown in FIG. 2 which is a diagrammatic perspective viewof the left handed spring 48. The springs are formed with a strong half49 and a light half 51. In manufacture, the light half is formed byskimming off part of a uniform strength spring and it is an effect ofthis that the diameter of the lightened half reduces a as shown. In thediagrammatic rows of rectangles representing the springs in FIG. 1, thestrong halves are represented by the larger rectangles.

The strong half of spring 46 engages with the internal surface of a bore52 of reel 13 while the light half engages around 62 biasesthe dog 61towards the position shown in cylindrical surface 53 provided on thereel 12. The strong half of spring 48 engages with the internal surfaceof a bore 54 formed in a projection from the frame 47 and the lighthalfengages around cylindrical surface 55 provided on the reel 12 on theaxially opposite side to the cylindrical surface 53. When the shaft isrotated in the sense of arrow G. wire is wound off from the larger reel12 onto the smaller reel 13.

The reels 14, 15 are provided with a right handed stepped helical coilspring 56 and a left handed stepped helical coil spring 57. Thearrangement is the inverse of that of reels 12. 13 as may be seen fromFIG. 1, except that for drive to the shaft 16 in the sense of the arrowG wire 58 is wound off from the smaller reel 14 and onto the larger reel15. In this condition, the mechanism of the upper reels 12, 13 isrecording while that of the lower reels 14, 15 isrewinding. When thedrive is reversed, the conditions of the two mechanisms are exactlyreversed and the mechanism of the upper reels 12, 13 is rewinding whilethat of the lower reels I4, 15 is recording.

Reversal of the drive is triggered automatically when one of the smallerreels becomes empty. The mechanism for this effect is illustrated inFIGS. 5 to 8 and will be described for the reel 13 only.

Pivotally mounted at 59 on the reel 13 is a dog 61. A spring FIGS. 6 and7 in which the end 63 of the dog moves in a path to engage against apivoted tig 64. Fixed to the dog is a loop of stiff wire 65 which isheld down close against the surface of the reel 13 by the wire 18wrapped round the reel as shown in FIG. 5. When the loops 65 is helddown in this way the dog 61 is held against the bias of spring 62 out ofthe path in which it engages the tig 64.

However, when the loop 65 is released on the unwinding of the last loopof wire 18, the dog 61 strikes the tig 64 and pivots .the tig 64 asillustrated in FIGS. 6 and 7.

The tig 64 is biassed by a toggle spring (not shown) so that once movedover center by the dog 61 it completes the movement to the FIG. 7position with a snap action. The tig 64, thus moved, operates areversing microswitch 66. However, to avoid or reduce the possibility ofthe switch contacts teetering a differential land cam 67 is interposedbetween the tig 64 and the microswitch operating button 68. The effectof this is for the toggle switch action of the tig 64 to double thetoggle action of the button 68 inherently built into the microswitch.The differential land cam 67 has three portions 67a, 67b and 67c. Whenthe button 68 is engaged by portion 67a, the microswitch is in onecondition, say off. When the button 68 is engaged by portion 67c, themicroswitch is on. When the button 68 is engaged by the intermediateportion 67b the microswitch remains in the state it was previously in,Le. the movement of the button 68 caused either as it rides up fromportion 67 a to 67b or as it rides down from portion 67c to portion 67bof the cam 67 is insufficient to move the microswitch toggle overcenter.The engagement of the button 68 by this intermediate portion 67b isarranged to occur during the overcenter movement of the tig 64. Thus,switching of the microswitch 66 only occurs after the tig 64 has goneover center so that the microswitch is rushed through the dangerous lowpressure instant just before breaking occurs. As may be seen from FIG.8, the tig 64 and the cam 67 are mounted on a spindle 69. A second tig,not shown is mounted on this spindle for actuation by a correspondingdog on the reel 14. The dog on the reel 14 faces in the opposite senseto the dog 61, so that the tigs and cam 67 are reset and rereversaltakes place when the reel 14 becomes empty of wire.

The wire is arranged so that there is always more wire on the largerreels l2 and 15 than on the smaller reels 13 and 14. In this wayreversal is always initiated by the emptying of one of the smaller reelsbefore one of the larger reels becomes empty.

Since the dogs cannot operate the tigs in the opposite sense I to thatintended, it is not possible to provide for independent externalreversal. The difficulty may be overcome by coupling the externalreversing switch to the tigs 64 so that they are also switched over.Alternatively the dogs or tigs or both for each reelmay be doubled.

The operation of the reeling mechanism when drive is applied to theshaft 16 and, via reduction gears, to the heart cam 38, is as follows:

When the shaft 16 is rotated in the sense of arrow G in FIG. 1, thesmaller reel 13 winds wire 18 onto itself. The surface of the bore 52 inthe reel 13 acts on the right handed helical coil spring46 so as to tendto unwind the spring. This action increases the interaction between thestrong half of the spring 46 and the bore 52, in practice looking thespring to the bore. However, the action reduces the interaction betweenthe light half of spring 46 and cylindrical surface 53, and in practicethe spring 46 slips over the surface 53. V

The larger reel 12 is caused to rotate in the same sense as the reel 13,but it does not have to rotate as fast. The action of the cylindricalsurface 55 on the left handed helical coil spring 48 is such as to tendto wind up this spring 48. In practice this locks the spring 48 to thereel 12. The winding up action also reduces the interaction between thestrong half of spring 48 and the internal surface of bore 54, thuspermitting slip between these components as is necessary for the reel 12to rotate. However, the frictional drag exerted by the strong half ofspring 48 is greater'than the drive friction exerted by the light halfof spring 46 on the reel 12. The excess frictional drag on the reel 12provides the tension in the wire and the parameters of the springs 46and 48 are chosen to give the desired magnitude to this tension. Forconvenience of description, the action of the light halves of thestepped helical coil springs, which is in the nature of a ratchetaction, is referred to as locking in one sense (the sense in which theyare wound up onto the cylindrical surfaces on which they engage) andslipping (or ratchetting) in the other sense (the sense in which thedrive tends to unwind the springs from engagement with the cylindricalsurface). The action of the strong halves of the stepped helical coilsprings is referred to as locking in one sense (in which the drive tendsto unwind them into tighter engagement with their respective bores) anddragging in the other sense (in which the drive tends to wind up thesprings).

For drive in the sense of arrow G in FIG. 1, the lower reels 14, 15 arerewinding. That is, wire is wound onto reel 15 off from reel 14. Thecondition of the stepped helical coil springs, are as follows: thestrong half of right handed helical coil spring 56 is dragging and thelight half is locking: the Iighthalf of left handed helical coil spring57 is slipping and the strong half is locking. Thus, it will be seenthat the drive force to the reel 15 derived from the drag between thestrong half of spring 56 and the reel 14, is greater than the resistancederived from the slipping interaction between the light half of spring57 and the reel 15. However, the reel 15 does not have to rotate as fastas the reel 14 because the wire is wound on at ,a larger diameter.Consequently there is dragging slip between reel 14 and strong half ofspring 56 because the reel 15 is held back by the wire 58. Again, thetension in the wire is provided by the excess of the drag between reel14 and spring 56 over the slipping resistance between reel 15 and spring57.

On reversal of the drive, the conditions of the upper and lower reelingmechanisms are exactly reversed.

The reduced drive to heart cam 38 produces a slow reciprocating tiltingof the platform 22 and this action causes the wire to run onto, or offfrom, the reels in even axially extending layers. The setting of thepulleys 19, 21, 24 and 25 has to be very accurate in relation to thereels 12, 13, 14 and 15 respectively and independent adjustment of thespacing of each pulley from the plate on which it is mounted is notreadily achieved because the required spacing of the wire from theplates is determined by the recording heads. However, the conditions arecritical and some provision for adjustment is found to be necessary.

In this example, the adjustments provided are as follows:

I. Axial movement of the stack of reels 12, 13, 14 and 15,

2. Adjustment of the mean tilt of the platform (c.f. arrows 43 in FIG. 3anddescription above) 3. Lateral adjustment of the plates 28 and 32 onthe platform 22 (cf. arrows 29 in FIG. 4 and description above).

The facilities provided by these three adjustments lS best understood byreference to the effects they produce respectively on an apparatus whichis initially producing perfect layering.

In FIG. 9 on the left-hand half of the FIG. the hatched regionsrepresent perfectly layered wire with the mechanisms fully wound in onesense The right-hand half of FIG: 9 shows the corresponding perfectlywound conditions with the mechanisms fully wound in the opposite senseFIG. 10 is a condensed diagrammatic representation of this perfectlayering condition. This FIG. 10 form of representation is employed inFIGS. 11 to 16.

FIG. 11 shows the effect on the layering of wire in a mechanismpreviously producing perfect layering if the stack of reels is moveddownwardly (as seen in the FIGS.) relative to the platform 22. That iseach reel is fuller at the top than at the bottom.

FIG. 12 shows the effect of the layering of wire in a mechanismpreviously producing perfect layering if the mean tilt of the platform22 is moved clockwise (as seen in FIG. 3). That is, reels l2 and 14 arefuller at the top than the bottom and reels 13 and are fuller at thebottom than at the top.

FIG. 13 shows the effect on the layering of wire in a mechanismpreviously producing perfect layering if the plate 28 is moved to theleft (as seen in FIGS. 3 and 4). That is, reels 12 and 13 are fuller atthe top than the bottom and reels 14 and 15 remain perfect.

Many layering faults can be corrected by employing selected combinationsof these three adjustments. However some faults cannot be corrected butit is usually possible to spread their effect evenly onto the four reelsand thereby reduce the seriousness of the faults.

An example is shown in FIGS. 14 to 16 where reels l3, l4 and 15 areperfectly layered but the layering of reel 12 has an unacceptable fault.The seriousness of a fault may be represented numerically and 0 is usedto indicate no fault, I, 2, 3, 4 to indicate faults of increasingseriousness. In this example a fault level of I on any reel can betolerated but greater fault levels cannot be tolerated.

Thus, assuming the layering of reel 12 in FIG. 14 has a fault level of4, movement of the plate 28 to the left (as seen in FIGS. 3 and 4) canproduce the condition shown in FIG. 15 in which the fault is sharedbetween reels l2 and 13. Each of these reels then has a layering faultlevel of 2.

If the platform 22 is then tilted clockwise (as seen in FIG. 3) thefault is shared between all four reels as shown in FIG. 16. Each of thefour reels then has a layering fault level of l, which can be tolerated.

The mechanism of this example is particularly suitable for withstandingaircraft environment entailing, inter alia prolonged vibration at a widerange of frequencies. In this respect the doubling of the toggle effectfor the reversing microswitch 66 is important. Under static conditions amicroswitch does not dither but under certain conditions of vibration aswitch, when in position just prior to switching, can permit thecontacts to resonate and this, can cause arcing. Such arcing seriouslyreduces the life of the switch, creates electrical noise and can weldthe contacts together or in some cases burn them causing highresistance. These serious problems are overcome or at least to someextent avoided in the arrangement of the foregoing example.

The invention is not restricted to the details of the foregoing example.For instance, although the differential land cam arrangement ispreferred for effecting the doubling of the toggle action of themicroswitch 66, other methods may conveniently be employed such as, forexample coupling the switching force to the button 68 by a low ratesecondary spring which amplifies the distance moved before switchingpressure is attained. The stepped helical coil springs need notnecessarily be manufactured by skimming off part of a uniform strengthspring but may for example, be manufactured by initially making thestrong and light halves separately and then joining them.

lclaim:

l. A mechanism for reeling an extended member off a first reel onto asecond reel, the maximum diameter at which the extended member is woundonto one reel being less than the minimum diameter at which the extendedmember is wound off the other reel, said mechanism comprising reversibledrive means directly coupled to the said first reel; a slipable clutchcoupling said reversible drive means to the said second reel; brakemeans for acting on said second reel, the drag torque of the said brakemeans exceeding the drive torque of the said slipable clutch when thereversible driving means drives said first reel in a first sense forwinding the extended member onto the said first reel from the saidsecond reel; the drive torque of the slipable clutch exceeding the dragtorque of the brake means when the reversible drive means drives thefirst reel in a sense opposite the first sense.

2. A mechanism as claimed in claim 1, further comprising shaft means,said two reels being coaxially mounted on said shaft means, means keyingsaid first reel to said shaft and bearing means supporting said secondreel for rotation about said shaft.

3. A mechanism as claimed in claim 1, wherein the slipable clutchcomprises a stepped helical coil spring coupled between the reels.

4. A mechanism as claimed in claim 1, further including a supportingframe and wherein the brake means comprises a stepped helical coilspring coupled between the supporting frame and the said second reel.

5. A mechanism as claimed in claim 1 wherein the slipable clutchcomprises a stepped helical coil spring having a first stepped part anda second stepped part, the diameter of the first stepped part being oflarger diameter than the second stepped part in which the first steppedpart of the coil spring engages a bore in the first reel and the secondstepped part of the coil spring engages a cylindrical surface of saidshaft means.

6. A mechanism as claimed in claim 4, wherein the brake means comprisesa stepped helical coil spring of opposite hand to that comprising saidslipable clutch, said stepped helical coil spring brake means having afirst stepped part and a second stepped part, the stepped helical coilspring brake means first stepped part being of larger diameter than thestepped helical coil spring brake means second stepped part in which thesecond stepped part of the coil spring engages a cylindrical surface ofthe said shaft means and the first stepped helical part engages a borein the said frame member.

7. A mechanism for reeling an extended member, as claimed in claim 1,incorporated in a magnetic wire recording mechanism.

8. A mechanism for reeling an extended member, as claimed in claim 1,wherein means are provided for automatically reversing the direction ofdrive to the said one reel after a predetermined amount of reeling fromone reel onto the other has taken place.

9 A mechanism for reeling an extended member as claimed in claim 1,wherein guide pulleys are provided for guiding wire, tape or a likeextended member off from one reel onto a coaxially mounted reel, whichguide pulleys are mounted on a single platform, and whereinreciprocating means reciprocate the platform to cause the extendedmember to form into, or run easily from, even axially extending layerson the reels.

10. A mechanism for reeling an extended member as claimed in claim 9,wherein adjusting means adjust the setting of relative location and/ororientation of the platform and reels for applying correction tolayering faults.

11. A mechanism for reeling an extended member as claimed in claim 1,wherein an automatic switching device comprises a switch member on areel, biasing means for biasing said switch member into a switchactuating position, said extended member wound on the reel holding saidswitch member against the bias and whereby the releasing means releasingthe switch member into a switch actuating position is the last layer ofextended member.

provided comprising an operating member and an operated member both ofwhich are arranged and biassed to be movable over the center with atoggle action between off and on conditions. and coupling means betweenthe members arranged so that the operating member only acts upon theoperated member to move the operated member over center after theoperating member has moved over center.

1. A mechanism for reeling an extended member off a first reel onto asecond reel, the maximum diameter at which the extended member is woundonto one reel being less than the minimum diameter at which the extendedmember is wound off the other reel, said mechanism comprising reversibledrive means directly coupled to the said first reel; a slipable clutchcoupling said reversible drive means to the said second reel; brakemeans for acting on said second reel, the drag torque of the said brakemeans exceeding the drive torque of the said slipable clutch when thereversible driving means drives said first reel in a first sense forwinding the extended member onto the said first reel from the saidsecond reel; the drive torque of the slipable clutch exceeding the dragtorque of the brake means when the reversible drive means drives thefirst reel in a sense opposite the first sense.
 2. A mechanism asclaimed in claim 1, further comprising shaft means, said two reels beingcoaxially mounted on said shaft means, means keying said first reel tosaid shaft and bearing means supporting said second reel for rotationabout said shaft.
 3. A mechanism as claimed in claim 1, wherein theslipable clutch comprises a stepped helical coil spring coupled betweenthe reels.
 4. A mechanism as claimed in claim 1, further including asupporting frame and wherein the brake means comprises a stepped helicalcoil spring coupled between the supporting frame and the said secondreel.
 5. A mechanism as claimed in claim 1 wherein the slipable clutchcomprises a stepped helical coil spring having a first stepped part anda second stepped part, the diameter of the first stepped part being oflarger diameter than the second stepped part in which the first steppedpart of the coil spring engages a bore in the first reel and the secondstepped part of the coil spring engages a cylindrical surface of saidshaft means.
 6. A mechanism as claimed iN claim 4, wherein the brakemeans comprises a stepped helical coil spring of opposite hand to thatcomprising said slipable clutch, said stepped helical coil spring brakemeans having a first stepped part and a second stepped part, the steppedhelical coil spring brake means first stepped part being of largerdiameter than the stepped helical coil spring brake means second steppedpart in which the second stepped part of the coil spring engages acylindrical surface of the said shaft means and the first steppedhelical part engages a bore in the said frame member.
 7. A mechanism forreeling an extended member, as claimed in claim 1, incorporated in amagnetic wire recording mechanism.
 8. A mechanism for reeling anextended member, as claimed in claim 1, wherein means are provided forautomatically reversing the direction of drive to the said one reelafter a predetermined amount of reeling from one reel onto the other hastaken place.
 9. A mechanism for reeling an extended member as claimed inclaim 1, wherein guide pulleys are provided for guiding wire, tape or alike extended member off from one reel onto a coaxially mounted reel,which guide pulleys are mounted on a single platform, and whereinreciprocating means reciprocate the platform to cause the extendedmember to form into, or run easily from, even axially extending layerson the reels.
 10. A mechanism for reeling an extended member as claimedin claim 9, wherein adjusting means adjust the setting of relativelocation and/or orientation of the platform and reels for applyingcorrection to layering faults.
 11. A mechanism for reeling an extendedmember as claimed in claim 1, wherein an automatic switching devicecomprises a switch member on a reel, biasing means for biasing saidswitch member into a switch actuating position, said extended memberwound on the reel holding said switch member against the bias andwhereby the releasing means releasing the switch member into a switchactuating position is the last layer of extended member.
 12. A mechanismfor reeling an extended member, as claimed in claim 11, the extendedmember is wire, wherein the extended member is wire, said wire is woundoff from one reel onto another reel and the automatic switching devicereverses the drive to the reels when the said releasing means releasessaid switch member.
 13. A mechanism for reeling an extended member asclaimed in claim 1, wherein an electrical switching device is providedcomprising an operating member and an operated member both of which arearranged and biassed to be movable over the center with a toggle actionbetween off and on conditions, and coupling means between the membersarranged so that the operating member only acts upon the operated memberto move the operated member over center after the operating member hasmoved over center.